1. Field of the Invention
This invention relates to electronic supervisory and control apparatus for rotary machines.
High-power rotary machines, for example heat engines driving ships, generator sets, pumps and so on, require systematic control of certain operating parameters of which the values must not exceed certain limits, for example the temperature, the pressure of oil or of cooling water, or the speed in the case of heat engines.
In the case of breakdown it is of great interest to have a record of the number of operating hours of the machine and in particular a selective record of the running hours or number of rotations under abnormal operating conditions. Such records allow responsibility to be established in the case of breakdown and permit certain defects to be remedied.
In addition, it is of interest to automate the starting operations of heat engines, that must be commanded in sequence at exact times, as well as the procedures for emergency stopping in case of a defect, or for a normal stop.
2. Description of the Prior Art
At present the surveillance of heat engines is carried out by means of indicators or recorders for speed, running tests or of the values of some parameters, such as water or oil pressure or temperature, but there does not exist selective recording means retaining in a memory for example the number of operating rotations under certain abnormal conditions, so that in case of dispute as to the cause of a breakdown it is necessary to examine a large number of daily records, if they exist, to try to reconstitute the history of the machine.
As regards automation of starting or of stopping, these are generally effected by means of expensive circuits and relays contained in bulky cubicles. In practice, each cubicle is wired more or less by hand in order to carry out the automation shown on the basic diagram, which results in relatively long delays in manufacture, high charges for transport and handling of the cubicle and difficulties in adjustment during the initial setting-up and also for removing faults in the automation cubicles which can only be effected by qualified technicians.
On the other hand the existing apparatus for control and recording and the present automation cubicles consume a relatively large amount of energy which is taken initially from the mains or from a relatively high-power alternator driven by the machine.
Lastly, the existing arrangements require several movement sensors on the rotary machine to drive the tachymetric indicators and running-hour counters.
The object of the present invention is to provide electronic control arrangements for rotary machines that are much simpler than existing arrangements, of small bulk, may be mass-produced, are self-contained, require only a single movement sensor and allow the instantaneous speed to be known and also the recording of the total number of working rotations and the selective recording of the number of working rotations in different abnormal conditions and possibly combining several anomalies and which may automatically and sequentially control the starting and stopping operations.
Electronic arrangements for the control of a rotary machine are already known that comprise a low-power tachometer alternator driven by the machine, electronic shaping circuits connected to the alternator output which transform the alternating voltage supplied by the latter into rectangular impulses of constant duration, of which the frequency is proportional to that of the alternator, and electronic measuring circuits which count and record the rectangular pulses delivered per unit time (speed) and during predetermined periods (total operating time or time in over-speed or under abnormal conditions).
The object of the invention is achieved by means of an arrangement comprising in addition a rectifier connected to the alternator output which supplies the electronic circuits with low-voltage direct current.
Preferably, the arrangement further comprises a secondary battery which is connected to the rectifier output and which ensures the supply of direct current to the electronic circuits during starting of the rotary machine.
It is known to provide a rotary machine with circuits for selectively counting the number of machine rotations under abnormal conditions, for example with too-low oil or water pressure or above a predetermined speed.
In an arrangement in accordance with the invention, each selective counter circuit consists of at least one sensor, placed on the rotary machine, which automatically actuates a movable contact when an operating anomaly appears and a logic gate having several inputs. A first input of the gate is connected by way of a frequency divider to the output of the circuits for shaping the alternating voltage and the other inputs are each connected to one of the said movable contacts while the gate output is connected to a pulse counter.
An arrangement in accordance with the invention further comprises selective counter circuits for the number of operating rotations above a certain speed, which consist of a logic gate having an output that is connected to a pulse counter and at least two inputs of which one is connected to the output of the frequency divider and the other is connected to the output of a pulse integrator circuit.
An arrangement in accordance with the invention may additionally comprise circuits for automatically controlling the starting and stopping connected to outputs of frequency counters so that they control these operations sequentially.
The result of the invention is a novel product which forms a control arrangement for rotary machines. The advantages of this arrangement are as follows:
It is entirely contained in a unit of small bulk and of low weight, which may be soldered-up and therefore be made tamper-proof.
It is self-contained and does not require any external source of supply. In fact its consumption is very low, of the order of a few watts, and a very small permanent magnet tachometer alternator having a power of 10 to 20 watts is amply sufficient to supply the energy necessary for the control apparatus. A small dry battery having a capacity of a few ampere-hours is sufficient to store the energy necessary to feed the control circuits during the starting phase. Power consumption when the machine is stopped may readily be avoided by means of a relay that automatically isolates the control circuits that are not useful during stoppages. Lastly, if the controlled machine may remain idle for long periods, for example if it is a heat engine intended to drive an emergency generator set in case of supply failure, it is simple to connect to the mains a charger providing a continuous charge for the battery.
An important advantage of an arrangement in accordance with the invention lies in the fact that it allows all the functions of supervision, of recording and of automation, which were formerly obtained by means of indicating and recording apparatus and complex relay systems installed in specially wired control and automation cubicles, to be carried out simply and at less cost. It likewise permits simple selective recording combining several parameters, for example recording of the total number of operating revolutions, at a speed higher than 1000 r.p.m. with an oil pressure lower than a given value and a cooling-water temperature above a threshold level.
Such separate recordings of the more serious operating anomalies are very useful in case of breakdown to determine the true cause of the breakdown and to remedy it and likewise to establish the division of responsibility between constructor and user.
These selective recordings are obtained simply by combining, by means of logic gates, different items of information available in the arrangement, which allows selection, at no cost, of recordings appropriate to different machines while using arrangements that are largely identical.
Another advantage lies in the fact that it is possible to mass produce units containing all the circuits common to all the units, that is to say the battery and the circuits for charging it from the alternator (rectifier, transformer), circuits for pulse shaping, voltage dividers, counters, logic gates, connections for all the sensors placed on the machine and possibly only to modify certain connections to the inputs of the logic gates to obtain selective records corresponding to the particular application. Arrangements in accordance with the invention are therefore very flexible in application. On the other hand, as their cost and the charges for installation and wiring-up are reduced it is possible to contemplate the replacement of one unit by another in case of breakdown or even by way of preventive maintenance, which considerably reduces the cost of maintenance and of repair.
Another advantage of arrangements in accordance with the invention consists in the fact that the pulses from the frequency dividers after each starting of the rotary machine constitute a time-scale absolutely proportional by definition to the number of rotations made by the rotary machine and these pulses may readily be made use of to control automatically and in sequence the various phases of starting or of automatic delayed stopping of the machine, as well as the sequential putting into service of the different safety devices at required instants.
The following description refers to the drawings which represent (by way of example only) an embodiment of an arrangement in accordance with the invention.